It is the objective of this project to maintain a Pathology Reference Center and Repository and eight regional centers for the purpose of rendering diagnostic and research support to cooperative clinical studies pertaining to the therapy of malignant lymphomas. The Pathology Reference Center and the regional centers are headed by pathologists who have specialized in the diagnosis and study of neoplastic diseases of the lymphoreticular system and are making a joint effort to improve and refine the criteria for diagnosis and classification of these neoplastic diseases, thereby assuring the validity of the therapeutic results reported by their colleagues engaged in clinical studies. A number of ancillary research projects are being conducted. They are closely related to the primary aim of this project and supplement the clinical studies of the cooperative oncology groups whose investigative programs are supported by NIH grants.